Optical disk substrate and optical disk employing said optical disk substrate

ABSTRACT

An optical disk substrate which includes a plurality of sectors, tracks alternately formed into lands and grooves in a direction intersecting at right angles with a tracing direction during recording or reproducing of information, a first pit row having address information and formed at a specific position of the track of a predetermined one land or groove, and a second pit row having address information and formed in a different track neighboring the track formed with the first pit row in the tracing direction, and formed at a position deviated longer than a length of the pit row from the specific position. By the above arrangement, the address information can be read without interference, with reduction of waiting time for reading.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an optical disk usedsubstrate and an optical disk as a large capacity recording medium, andmore particularly, to an optical disk substrate and an optical diskcapable of being recorded at high density, and accessed from oppositesides or both faces.

2. Description of the Prior Art

Conventionally, the construction of an optical disk capable of beingaccessed from opposite sides or faces has been disclosed, for example,in Japanese Laid-Open Patent Publication Tokkaisho No. 60-57553, andcross sections thereof are shown in FIGS. 10(a), 10(b) and 10(c).

In FIGS. 10(a) and 10(b), the known optical disk includes substrates 101each made of a resin which transmits an irradiation beam, an opticalsubbing layer 102 provided on said substrate 101 for imparting a surfacesmoothness or forming tracks, etc. thereon, and an active layer 103, aspacer layer 104 and a reflective layer 105 further laminatedsequentially on said optical subbing layer 102 as shown.

In FIG. 10(a), the substrate 101 after the lamination as described aboveare bonded to each other through adhesive resin layers 107, with amechanical lining 106 of an aluminum plate or the like being heldtherebetween. Meanwhile, in the arrangement of FIG. 10(b), thesubstrates 101 after the lamination as stated above are directly bondedto each other through the adhesive resin layer 107. In the constructionof FIG. 10(c), after laminating the optical subbing layer 102, activelayer 103, spacer layer 104, and reflective layer 105 sequentially onthe substrate 101, another spacer layer 108 and an active layer 109 arefurther laminated to achieve an optically mirror symmetrical relation atthe reflective layer 105, with an overcoat layer 110 being furtherprovided as illustrated.

FIG. 11 is a schematic side elevational diagram showing an optical diskdevice of a dual sided access type, in which a double-sided disk 111 hasa recording capacity two times that of a single-sided disk, and iscapable of being simultaneously accessed on front and reverse faces bythe optical disk device. More specifically, the double-sided disk 111 ismounted on a rotary shaft 113 of a motor 112 for rotation in apredetermined direction, and by read/write heads 114 and 115 provided atthe front and reverse face sides of the double-sided disk 111, readingand writing of information are effected with respect to each face of thedisk 111.

Moreover, as one of the means for improving a recording density of anoptical disk, there has conventionally PG,4 been proposed a method forforming neighboring tracks alternately into lands and grooves as shownin FIG. 12, in which a single-sided disk 116 has its tracks formed bythe lands and grooves. For reading and writing information, as observedfrom an incident side of light, the read/write head 114 accesses thetrack for the groove, while the read/write head 115 accesses the trackfor the land, by which arrangement, the recording capacity may bedoubled as compared with the case where only the lands or grooves areutilized for the track.

In Japanese Laid-Open Patent Publication Tokkaihei No. 2-189743, thereis disclosed a system in which, in a dual sided access type opticaldisk, with respect to the neighboring tracks formed with the lands andgrooves as in the single-sided disk 116 in FIG. 12, the track for theland is accessed from the front face, while the track for the groove isaccessed from the reverse face.

As shown in FIGS. 10(a) and 10(b), in the conventional double-sideddisk, since the information of the track and address is provided in thesubstrate 101 or the optical subbing layer 102, such information of thetrack and address is completely independent on the front and reversefaces. However, due to the manufacturing process to bond twosingle-sided disks to each other after preparation thereof, manyman-hours are required for the manufacture, thus resulting in a costincrease. Meanwhile, when the optical disk as shown in FIG. 10(c) isadopted, there is an advantage in that the labor time is reduced forcost reduction. On the other hand, in the type where both faces of theoptical disk are simultaneously accessed, since rotating directions ofthe optical disk are opposite in the front and reverse faces, if theoptical disk has the constructions as explained with reference to FIGS.10(a) and 10(b), it becomes necessary to provide the substrate orsubbing layers of different formats. In order to solve such a problem,there has been proposed, for example, in Japanese Laid-Open PatentPublication Tokkaihei No. 4-64933, an arrangement in which two addressrows are provided in pairs so that one address may be read in adirection opposite in the scanning direction, but in this case, thelength of the address becomes undesirably longer.

In the case where the substrate for the conventional single-sided diskis to be accessed from both sides, heat interference occurs between thetracks on the front and reverse faces, if the same tracks are used forthe front and reverse faces. For example, in the optical disk of arewritable type, there is a problem that a recording mark disappears.

Such heat interference will not take place when different tracks areemployed on the front and reverse faces, but conventionally, since pitsfor the address information are located at approximately the sameposition, there has also been such a problem in that the information ofthe address is not easily read or tracking becomes unstable due tointerference with pits on the neighboring tracks.

Moreover, in the conventional practice, one track is divided into aplurality of sectors for allocation of the addresses, and in this case,since the neighboring tracks are located at approximately the sameposition, a waiting time for at least one sector is required for thechange-over of data on the front and reverse faces.

Even in the case of the one side access, there has also been aninconvenience in the conventional arrangement in that, in the opticaldisk utilizing both of lands and grooves for the tracks, since the pitsfor the address information are located at approximately the sameposition, interference occurs with respect to the pits of theneighboring tracks, thus making it difficult to read the information ofthe address or making the tracking unstable. Similarly, the problem thatthe waiting time at least for one sector is required for the change-overof the data between the lands and grooves, is also involved in thiscase.

SUMMARY OF THE INVENTION

Accordingly, an essential object of the present invention is to providean optical disk substrate and an optical disk in which a processingcircuit for address reading is simplified, without any interferenceduring reading of the address information, while waiting time forreading is reduced, and change-over at high speeds is made possible.

Another object of the present invention is to provide an optical disksubstrate and an optical disk of the above described type which aresimple in construction and accurate in functioning, and can be readilymanufactured on a large scale at a low cost.

In accomplishing these and other object of the present invention,according to one aspect to the present invention, there is provided anoptical disk substrate which includes a plurality of sectors, tracksalternately formed into lands and grooves in a direction intersecting atright angles with a tracing direction during recording or reproducing ofinformation, a first pit row having address information and formed at aspecific position of the track of a predetermined one land or groove,and a second pit row having address information and formed in adifferent track neighboring said track formed with said first pit row inthe tracing direction, and formed at a position which is spaced apart bya distance which is longer than length of the pit row from said specificposition.

In the above optical disk substrate, correspondence of the addressinformation to the concave and convex portions of said pit row isinverted between said neighboring tracks.

In another aspect of the present invention, the optical disk substrateincluding a plurality of sectors, track's alternately formed into landsand grooves in a direction intersecting at right angles with a tracingdirection during recording or reproducing of information, a first pitrow having address information and formed at a specific position of thetrack of a predetermined one land or groove, and a second pit row havingaddress information and formed in a different track neighboring saidtrack formed with said first pit row in the tracing direction, andformed at a position which is spaced apart by a distance which is longerthan a length of the pit row from said specific position, and at leastan active layer provided on said optical disk substrate.

In a further aspect of the present invention, the optical disk includesan optical disk substrate including a plurality of sectors, tracksalternately formed into lands and grooves in a direction intersecting atright angles with a tracing direction during recording or reproducing ofinformation, a first pit row having address information and formed at aspecific position of the track of a predetermined one land or groove,and a second pit row having address information and formed in adifferent track neighboring said track formed with said first pit row inthe tracing direction, and formed at a position which is spaced apart bya distance which is longer than a length of the pit row from saidspecific position, with correspondence of the address information to theconcave and convex portions of said pit rows being inverted between saidneighboring tracks, and at least two active layers and a reflectivelayer held between said active layers which are provided on said opticaldisc substrate.

In the arrangement according to the present invention as describedabove, the tracks are alternately formed into lands and grooves in adirection intersecting at right angles with a tracing direction duringrecording or reproducing of information, and the first pit row havingaddress information is formed at a specific position of the track of apredetermined one land or groove, and the second pit row having addressinformation formed in a different track neighboring said track formedwith said first pit row in the tracing direction, is formed at aposition which is spaced apart from the specific position, andtherefore, there is no interference during the reading of the addressinformation, with less waiting time for the reading.

Moreover, since the correspondence of the address information to theconcave portions and the convex portions is inverted between theneighboring tracks, the formats of the address information respectivelyread from the opposite sides of the disk are the same, and consequently,there is an advantage in that the processing circuit for the addressinformation becomes simple.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention willbecome apparent from the following description taken in conjunction withthe preferred embodiment thereof with reference to the accompanyingdrawings, in which;

FIG. 1(a) is perspective view of an optical disk substrate according toone preferred embodiment of the present invention;

FIG. 1(b) is a fragmentary top plan view showing on an enlarged scale, aportion indicated by X on the surface of the disk in FIG. 1(a) forexplaining construction of tracks and addresses thereof;

FIG. 1(c) is a fragmentary perspective view showing on a still enlargedscale, part of the tracks and addresses in FIG. 1(b);

FIG. 2(a) is a graphical diagram showing a tracking error signalaccording to a first embodiment of the present invention;

FIG. 2(b) is also a graphical diagram showing a single or one timedifferential signal of the above;

FIG. 3 is a schematic top plan view for explaining use of sectors for afirst embodiment of the optical disk substrate according to the firstembodiment of the present invention;

FIG. 4 is a fragmentary perspective view showing a second embodiment ofan optical disk substrate of the present invention;

FIG. 5 is a fragmentary cross section showing on an enlarged scale, anoptical disk according to a first embodiment of the present invention;

FIG. 6 is a fragmentary cross section showing on an enlarged scale, anoptical disk according to a second embodiment of the present invention;

FIG. 7 is a fragmentary cross section showing on an enlarged scale, anoptical disk according to a third embodiment of the present invention;

FIG. 8 is a fragmentary perspective view showing an optical disksubstrate according to a fourth embodiment of the present invention;

FIG. 9 is a schematic top plan view for explaining sectors of an opticaldisk substrate according to a fifth embodiment of the present invention;

FIGS. 10(a), 10(b) and 10(c) are cross sections showing three kinds ofconventional optical disks (already referred to);

FIG. 11 is a schematic side elevational view showing a conventionaloptical disk device of both side access type (already referred to); and

FIG. 12 is a fragmentary perspective diagram for explaining an opticaldisk device for simultaneously accessing a conventional single-sideddisk having lands and grooves (already referred to).

DETAILED DESCRIPTION OF THE INVENTION

Before the description of the present invention proceeds, it is to benoted that like parts are designated by like reference numeralsthroughout the accompanying drawings.

Referring now to the drawings, the present invention will be explainedfirst with respect to an embodiment of a double-sided optical disksubstrate which is to be accessed from front and reverse faces of thedisk.

In FIGS. 1(a), 1(b) and 1(c), there is shown an optical disk substrateaccording to a first embodiment of the present invention. On thesubstrate 1, substantially concentric tracks 2 for servo use are formedalternately by lands and grooves. In the tracks 2, addresses 3 writtenwith address information of the track 2 and sector are formed in a pitrow. The optical disk substrate 1 has such addresses 3 both on the landsand grooves. FIG. 1(c) shows the state of the addresses provided on thelands (at an A portion in FIG. 1(b)) and the state of the addressesprovided on the grooves (at a B portion in FIG. 1(b)). At these A and Bportions, correspondence of the concave portions and convex portions ofthe pits to the information is shown as being inverted. Directions atthe starting and ending of the information of the pits row are the sameboth in the A and B portions. For example, in the case where the lightbeam is moved from the left to right in FIG. 1(c), the left siderepresents the start of the information, and the right side denotes theend of the information.

By the above arrangement, for example, in the case where irradiationlight from a mirror face side of the substrate 1 is projected onto thetrack having the address of A (i.e., the land side), and that from theopposite side is projected onto the track having the address of B (i.e.,the groove side), since the address information has the sameconfiguration with respect to the irradiation light, only one readingcircuit for the address information may be sufficient for the purpose.In this case, it may be so modified that the irradiation light from themirror face side of the substrate 1 is projected onto the track havingthe address for B, and that from the opposite side is projected onto thetrack having the address for A.

Meanwhile, in FIG. 1(b), the address 3 provided the groove are disposedthrough deviation in the circumferential direction. This arrangement isnecessary, because if the addresses 3 are present in the positions whichcoincide in the circumferential direction in the tracks for the landsand grooves, for example, in the case where condensed light spot isdirected onto the position of the address 3 in the track for the land,the end portion of the condensed light spot is also projected onto theposition of the address 3 in the track for the groove so as to give riseto the interference of the light, thus making it impossible to read theaddress information correctly.

Subsequently, control performance for the tracking will be investigated.By way of example, there will be considered a case where a substrate inwhich one track includes 18 sectors is rotated at 1,800 r.p.m. Thecontrol frequency bandwidth for the tracking is set to be below 3 KHz.When the addresses are arranged at equal intervals on the track by thenumber of sectors, the frequency for detecting the address is 540 Hz perone track, and circularity and eccentricity of the track (an amount ofdeviation between a rotational center of the disk and the center of thetrack) can be fully followed thereby.

Here, the address pit row acts as disturbance of signals in the casewhere tracking is effected. Generally, the control becomes difficult ifthe disturbance takes place for a time period longer than four times thecontrol frequency bandwidth of the tracking, and the time period will be83 μs in this example. Therefore, if the length of the address pit rowis selected to be 50 μs in the length of signal, there will be noproblem in the tracking control performance.

Then, it is necessary to identify the track provided on the substrateduring the tracking, and in the present invention, it is required todistinguish the land and groove in a manner as described hereinbelow.

Due to the deviation between the track center and the rotational centerwhen the tracking control is not effected, the tracking error signal hasa wave form as shown, for example, in FIG. 2(a), which represents thetracking error signal equivalent to one round of the substrate. Forexample, in the tracking control based on a push-pull method, adifference signal of returning light from the substrate is set to be thetracking error signal through employment of a binary detector. The statethat the tracking error signal becomes positive or negative shows thatthe center of the beam spot has been deviated from the center of thetrack for the land or groove formed in the substrate. Here, on theassumption that the position of a zero crossing point rising at theright represents the center of the track for the groove, the position ofa zero crossing point lowering at the right shows the center of thetrack for the land. Accordingly, in the case where the track for thegroove is accessed by observing the substrate from the incident side ofthe light, it may be so processed to detect the zero crossing pointrising at the right of the tracking error signal so as to displace apick-up to said position for effecting control. For such detection andholding of the zero crossing point, processing may be so effected thatthe maximum value of a single differential signal of the tracking errorsignal is detected, and this single differential signal of the trackingerror signal is controlled to be of the largest value at all times. FIG.2(b) shows the single differential signal of the tracking error signal.Similar control may be effected in the case where the land portion is tobe accessed by observing the substrate from the incident side of light,with only the polarity being reversed.

According to the present invention, the lands and grooves are utilizedas the tracks, and the amount of deviation in the positions of thetracks for the lands and grooves is set to be of a predetermined valuein the range of 1/4 sector to 3/4 sector. This range is considered to besuitable for reducing the waiting time for the change-over of the databetween the lands and grooves, and the most preferable deviation amountis 1/2 sector. Generally, from the viewpoint of simplification of themechanical system, the two read/write heads disposed at the front andreverse sides of the optical disk are designed to be displaced in thesame radial direction. Thus, in the case where the data on the front andreverse sides are accessed in association with each other, the waitingtime required for the change-over of the data at the front and reversesides becomes the time in which the beam is displaced in the deviationamount of the sector. Moreover, in the case where the access is to bechanged over between the tracks provided at the front and reverse sides,the deviation amount in the position of the address should be madelonger than the length of the address. This is necessary since theaddress of a next track is read after the address of the previous trackhas been read. The reading of the address is processed in the real time,and consequently, data processing at high speed becomes possible.

FIG. 3 shows an example for use of the sectors in the optical disksubstrate for a first embodiment of the present invention.

Solid lines in the radial direction show the positions of addresses inthe sectors on the front face, while dotted lines represent thepositions of addresses in the reverse face, and the amount of deviationin the sectors between the front and reverse faces is set to beequivalent to 1/2 sector. In the above case, when the sectors on thefront and reverse faces are accessed in the order as shown in FIG. 3,the waiting time required for the change-over between the front andreverse faces is to be the time for the disk to move through the amountequivalent to 1/2 sector. In the case where the addresses are in thesame position on the front and reverse faces as in the conventionalarrangement, time for the disk to move through the amount equivalent toone sector is required for the change-over between the front and reversefaces.

The purpose for disposing the pit rows of the addresses on the radiallines passing through the center of the substrate is to reduce the timerequired for the retrieval by specifying the position on the disk fromthe address information.

Subsequently, the reason why the tracks of the substrate are formed bythe lands and grooves will be described.

In the tracking systems for the optical disk having the flat tracks,there is a sample servo system, in which pit row showing the positionsof tracks are provided through a predetermined interval. Such pit rowsare required to be provided at frequencies of 40 to 50 MHz for thetracking control, and formed as the sector in one set with the addressinformation. In this case, if the sector positions are provided to bedeviated between neighboring tracks, the influence of the pit row of thesector in the neighboring track acting as disturbance with respect tothe tracking control is received in the frequencies at 40 to 50 MHz, andthus, the tracking becomes unstable. In other words, by effecting thetracking through utilization of the lands and grooves of the tracks, thenumber of pit row to be provided on one track can be reduced to agreater extent.

The substrate 1 as shown in FIGS. 1(a) to 1(c) is made of a resin suchas PMMA (polymethal methacrylate), polycarbonate, polyolefin or thelike, or a glass material. In the case of a resin material, thesubstrate may be formed by the injection compression molding method byusing a metallic stamper of nickel or the like. Formation of concave andconvex portions on the stamper may be effected, for example, by a methodof employing two light beams having the same spot diameter. In the firstplace, on a polished glass original plate like a disk, a photoresistlayer is formed in a uniform film thickness by using a spin coater, andbaked. Then, two light beams having the same spot diameter and strength,with wavelength in the sensitizing band of the photoresist are projectedonto the photoresist surface. These two light beams are disposed througha space equivalent to a distance between the neighboring tracks, in adirection at right angles with the displacing direction of the glassoriginal plate. In this case, it is preferable that the two light beamsshould be spaced apart in the circumferential direction in order toavoid interference therebetween, and these two light beams areindependently modulated through synchronization, so as to expose thephotoresist. In such a manner, neighboring tracks provided with respectto the light beams different in the incident directions aresimultaneously formed. At this time, in order to focus on thephotoresist face, another light beam having a wavelength outside thesensitizing band of the photoresist is employed.

In the case where the tracks are provided in the concentric shape, afterexposure of the amount for one circumference, the irradiating lightsource is mechanically displaced by an amount equivalent to two tracksof the land and groove. Meanwhile, when the tracks are to be spirallyprovided, mechanical feeding is effected at a constant feeding speed sothat after displacement of one circumference, the track for the landcomes to the position of the next track for the land, and the track forthe groove, to the position of the next track for the groove,respectively. After the exposure, development of the photoresist iseffected. In the case where the photoresist is of a positive type, theexposed portion is dissolved by an alkaline developing solution, whilethe portion not exposed remains as is. Thereafter, the glass originalplate is washed and dried, and after a silver mirror finish is effected,it is subjected to nickel electro-plating for subsequent separation toform the stamper. Here, before the nickel electro-plating, sputterplating of nickel or non-electrolysis plating may be effected as in thegenerally known practice. Before attaching to the metal mold, thereverse face of the stamper is polished for smoothness and uniformthickness of the substrate to be molded.

In the case of a glass substrate, there are a sol-gel method on onehand, in which a material in a fluid state is poured into a metal moldfor hardening by using the stamper as in the resin substrate, andanother method by etching on the other hand. The etching method includesthe steps of polishing a glass substrate of a flat disk, washing theglass substrate, applying a photoresist thereonto, spin coating thereof,subjecting the glass substrate to baking treatment, exposing to thelaser beam, and after developing, effecting etching by using thephotoresist remaining on the glass substrate as a mask. In the case ofthis method also, during the exposure by the laser beam, exposure may beeffected by means similar to that in the stamper forming as describedearlier, i.e., the means which employs the three light beams, one lightbeam with the wavelength outside the sensitizing band of thephotoresist, and the others with the wavelength within the sensitizingband thereof.

FIG. 4 shows address pit rows for a second embodiment of an optical disksubstrate of the present invention. The tracks are provided by the landsand grooves so as to be in the concentric shape or spiral shape. In thissubstrate also, the positions of the address pit rows are spaced apartin the circumferential direction between the tracks forming the landsand the tracks forming the grooves as viewed from one face side. Thepositions of the address pit rows in the tracks forming the lands andthose forming the grooves are arranged on the radial lines passingthrough the center of the substrate in the plurality of tracks. Thisarrangement is intended to access the desired position on the substrateat high speed, since the positions of the tracks and sectors arespecified.

Meanwhile, for changing-over the access between the tracks provided onthe front and reverse faces, the amount of deviation in the positions ofthe addresses of the tracks for the lands and grooves is required to belonger than the length of the address in order to read the address ofthe subsequent track after having read the address of the previoustrack. Specifically, such deviation amount of the addresses is in therange from 1/4 sector to 3/4 sector as described earlier, and morepreferably, 1/2 sector. In the case of the double-sided disk forsimultaneous access on the front and reverse faces, the waiting timenecessary for the change-over of the access on the front and reversefaces becomes the deviation amount of the sectors. Accordingly, thewaiting time may be made shorter than the conventional displacing timeof the disk for one sector.

In the optical disk substrate of the second embodiment as describedabove also, the correspondence of the concave and convex portions of thepits for the addresses to the information is inverted between the trackfor the lands and the track for the grooves in the similar manner as inthe first embodiment. The directions of the starting and the ending ofthe information are the same both in the A portion and B portion. Thisis owing to the fact that, for example, in the case where theirradiation light is projected onto the track of the address for A fromthe mirror face side of the substrate 1, and onto the track of theaddress for B from the opposite side, the correspondence of the addresspits to the information becomes the same when observed from theirradiation light side, and therefore, one reading circuit of theaddresses is sufficient for the purpose. It is needless to say that thearrangement may, for example, be so modified that the irradiation lightfrom the mirror face side of the substrate 1 is projected onto the trackof the address for B, and that from the opposite side is projected ontothe track of the address for A.

Although the address pit rows act as the disturbance for the trackingcontrol in this embodiment also, such address pit rows are spaced apartin the circumferential direction between the tracks for the lands andthe tracks for the grooves in the similar manner as in the firstembodiment, and the detecting frequency for the address is low, with ashorter time occupied by the address in the signal, and thus, theaddresses can be read stably, without affecting the trackingperformance.

The distinguishment between the tracks for the lands and the tracks forthe grooves during the tracking may be readily effected by utilizing thetracking error signal and the single differential signal of the trackingerror signal as described earlier with reference to the firstembodiment. Since this identification method does not require one toread the address information, it may be processed in real time in thesearch or retrieving function for access to the arbitrary tracks andsectors.

According to the present invention, the pit rows of the addressinformation are provided by the lands and grooves formed with a largelevel difference or by the concave and convex portions on the tracks forthe lands and grooves. By such an arrangement, the influence due to thedisturbance in the address pit rows is reduced. Therefore, the substrateof the present invention is effective even in the case of a ROM in whicha data portion is also constituted by the pit rows.

The substrate of the present invention is made of a resin or a glassmaterial. In the case of the resin material, the substrate is formed bythe injection compression molding method by using a stamper. For thestamper, a photoresist layer is first formed in a uniform film thicknesson a polished glass original plate like a disk by using a spin coater,and baked. Then, by applying focusing with a light beam having awavelength outside the sensitizing band of the photoresist, continuousexposure is effected by a light beam with a wavelength within thesensitizing band of the photoresist, for subsequent development to formalternately continuous tracks for the lands and tracks for the grooves.

The pit rows are not first formed, since it is necessary to effect thetracking control by using the tracks for the lands and grooves in thenext step.

Thereafter, the photoresist is again applied, and the photoresist layeris formed into a uniform film thickness by using a spin coater, andbaked. This time, the tracks for the lands or the tracks for the groovesare subjected to the tracking control by the light beam with awavelength outside the sensitizing band of the photoresist, togetherwith focusing applied. Then, two light beams having the same spotdiameter and strength, with wavelength in the sensitizing band of thephotoresist are projected onto the photoresist surface. These two lightbeams are disposed through a space equivalent to the distance betweenthe neighboring tracks in a direction at right angles with thedisplacing direction of the glass original plate. In this case, it ispreferable that the two light beams should be spaced apart in thecircumferential direction in order to avoid interference therebetween,and these two light beams are independently modulated throughsynchronization, so as to expose the photoresist for subsequentdevelopment. In such a manner, neighboring tracks provided with respectto the light beams different in the incident directions aresimultaneously formed. As a result, on the tracks for the lands andgrooves provided through a large difference in level as shown in FIG. 4on the glass original plate, the address pit rows can be formed byconcave and convex portions. Thereafter, the glass original plate iswashed and dried, and after a silver mirror finish is effected, it issubjected to nickel electro-plating for subsequent separation to formthe stamper. Here, before the nickel electro-plating, sputter plating ofnickel or non-electrolysis plating may be effected as in the generallyknown practice. Before attaching to the metal mold, the stamper ispolished at its reverse face for smoothness and uniform thickness of thesubstrate to be molded.

Meanwhile, in the case of the glass substrate, there are available thesol-gel method and the etching method as referred to earlier. Theetching method includes the steps of polishing a glass substrate of aflat disk, washing the glass substrate, applying a photoresistthereonto, spin coating thereof, subjecting the glass substrate tobaking treatment exposing to the laser beam, and after developing,effecting etching by using the photoresist remaining on the glasssubstrate as a mask. In the above case where the etching is effected,the step of forming the stamper and steps up to the developing of thephotoresist are the same, and the step of forming the concave and convexportions on the glass original plate by etching is added thereafter. Inthe case of preparing the glass substrate also, the alternatelycontinuous tracks for the lands and the grooves are first formed, andthen, the concave and convex pits are formed in the tracks for the landsand grooves.

Subsequently, results of investigation made into the cross-talk by theneighboring tracks under such conditions that the width of the tracksfor the lands and grooves is 0.8 μm, wavelength is 830 nm, and aperturenumber of an object lens is 0.5, will be described hereinbelow.

In the case where the information in the data region utilizes phasedifference of light as in a ROM, the crosstalk with respect to theneighboring track was reduced below -30 dB, when the level differencebetween the track for the land and the track for the groove was largerthan 200 nm. On the other hand, when the information in the data regionutilizes the difference of the reflection of light in the data region,the crosstalk with respect to the neighboring track was reduced below-30 dB, when the level difference between the track for the land and thetrack for the groove was larger than 50 nm.

FIG. 5 shows a fragmentary cross section of the optical disk accordingto a first embodiment of the present invention utilizing the disksubstrate as illustrated in FIG. 1 or 4.

In FIG. 5, the optical disk includes a substrate 1, and a dielectriclayer 4, an active layer 5, a dielectric layer 6, a reflective layer 7,a dielectric layer 8, an active layer 9, and a dielectric layer 10sequentially laminated on the dielectric layer 4 in that order, on thesubstrate 1 by a vacuum film forming method, e.g., a sputtering methodand a transparent flat plate 12 further applied onto the dielectriclayer 10 through an adhesive layer 11, so as to provide a mirrorsymmetrical relationship at said reflective layer 7. As described above,since the optical disk according to the present embodiment may be formedonly by the steps similar to those in the conventional single-sidedoptical disk, labor time during manufacture can be lowered for costreduction.

For the active layers 5 and 9, for example, a dyeing material, aphase-change material, and an optical magnetic material, etc. aresuitable. Since the active layers for 5 and 9 are optically cut off bythe reflective layer 7, marks formed in the active layers 5 and 9 may beread without interference.

Meanwhile, according to the optical disk of the present invention, themirror-symmetry is established at the reflective layer 7 with respect tothe light irradiated onto the substrate 1, the processing of the signalsystem becomes the same on the both faces of the disk, and thus, thecircuit system may be simplified.

Moreover, since the positions of the addresses 3 formed in the pits arespaced apart in the circumferential direction, there is no possibilitythat interference occurs during reading of the addresses. Particularly,when the amount of spacing of the addresses is set to be in the range of1/4 sector to 3/4 sector, and preferably, at 1/2 sector, the waitingtime for change-over between the front and reverse faces is shortenedfrom the conventional displacing time of the disk for one sector duringassociated use of the front and reverse faces, and thus, high speedaccess is made possible.

It is to be noted that in the present embodiment (FIG. 5), although theflat plate 12 is employed for the surface at one side, this may ofcourse be replaced by another substrate 1. Moreover, the dielectriclayers 4 and 10 or dielectric layers 6 and 8 may be dispensed withdepending on the requirement.

FIG. 6 shows a fragmentary cross-section of an optical disk according toa second embodiment of the present invention, in which the disksubstrate 1 as shown in FIG. 4 is employed.

In FIG. 6, the optical disk includes a substrate 1, and tracks for landsand grooves formed at approximately the same width on the substrate 1 ina concentric or spiral configuration. On the substrate 1, not only theaddresses, but also information of data (i.e., ROM) are provided by thepits of a system in which correspondence of the concave and convexportions to the information is inverted respectively at the lands andgrooves. Moreover, information pits such as track addresses and sectoraddresses, etc. are also provided at different positions in thecircumferential direction in the lands and grooves. On the substrate 1,a reflective layer 7 is formed, and a transparent flat plate 12 isapplied thereon through an adhesive layer 11. Here, the pits for thelands and grooves provided on the substrate 1 are required to beincreased in the difference of heights between the lands and grooves soas to prevent optical interference therebetween. A level differencelarger than 200 nm was necessary as a result of experiments under theconditions that the width of the track for the land and groove was 0.8μm, wavelength of the irradiation light was 830 nm, and aperture numberof the objective lens was 0.5.

When the optical disk is observed with respect to the irradiation lightfrom the side of the substrate 1, and the irradiation light from theside of the flat disk 12, both are the same optically, and therefore,reproduction of information can be effected by the same signalprocessing circuit system.

Moreover, since the manufacturing process of the optical disk accordingto the present embodiment is similar to that of the conventionalsingle-sided optical disk, labor time required therefore may bedecreased for a cost reduction cost.

Furthermore, when the amount of spacing in the circumferential directionof the addresses provided on the lands and grooves is set to be in therange of 1/4 sector to 3/4 sector, and more preferably, to 1/2 sector,the waiting time for change-over between the front and reverse faces isshortened from the conventional displacing time of the disk for onesector during associated use of the front and reverse faces, and thus,high speed access is made possible.

Although the flat plate 12 is employed for the surface at one side, thismay of course be replaced by another substrate 1.

FIG. 7 is a fragmentary cross section of an optical disk according to athird embodiment of the present invention, in which the disk substrate 1as shown in FIG. 4 is also employed.

In FIG. 7, the optical disk has a substrate 1, and tracks for lands andgrooves formed at approximately the same width on the substrate 1 in aconcentric or spiral configuration. On the substrate 1, information pitsof data are provided on the track for the lands.

Moreover, information pits such as track addresses and sector addresses,etc. are provided at different positions in the circumferentialdirection in the lands and grooves. In these information pits,correspondence of the concave and convex portions to the information isinverted respectively at the lands and grooves. On the substrate 1, areflective layer 7, a dielectric layer 8, an active layer 9 and adielectric layer 10 are sequentially formed and a transparent flat plate12 is applied thereon through an adhesive layer 11. Here, the pits forthe lands and grooves provided on the substrate 1 are required to beincreased in the difference of heights between the lands and grooves soas to prevent optical interference therebetween. A level differencelarger than 200 nm was necessary as a result of experiments under theconditions that the width of the track for the land and groove was 0.8μm, wavelength of the irradiation light was 830 nm, and aperture numberof the objective lens was 0.5.

Here, the amount of the reflective light is utilized for the detectionof the signal, and thus, it is desirable to make the recording mark andthe pit optically equal. By such arrangement, the signal processingcircuit for the reproduction may be reduced to one.

Moreover, since the manufacturing process of the optical disk accordingto the present embodiment is similar to that of the conventionalsingle-sided optical disk, labor time required therefore may bedecreased for a cost reduction.

Furthermore, when the amount of spacing in the circumferential directionof the addresses provided on the lands and grooves is set to be in therange of 1/4 sector to 3/4 sector, and more preferably, to 1/2 sector,the waiting time for change-over between the front and reverse faces isshortened from the conventional displacing time of the disk for onesector during associated use of the front and reverse faces, and thus,high speed access is made possible.

It is to be noted that although the flat plate 12 is employed for thesurface at one side, this may of course be replaced by another substrate1, while the dielectric substrates 8 and 10 may be dispensed with.

It should also be noted here that the layers to be formed on thesubstrate 1 may be so modified that the dielectric layer, the activelayer, the dielectric layer, and the reflective layer are formed on saidsubstrate 1 in the order opposite to that in the embodiment of FIG. 7.

Additionally, in the above embodiment, although the information otherthan the address (data information, etc.) is formed only on the trackfor the lands, this may be modified to be formed on the track for thegrooves alone.

In the foregoing, an explanation has been provided with respect to theoptical disk substrate and the optical disk of the double-side facesimultaneously access type according to the present invention.

Subsequently, the optical disk substrate and the optical disk of asingle-side face access type is described.

In the first place, the optical disk substrate according to a thirdembodiment of the present invention will be explained, which is similarin appearance to the substrate 1 as shown in FIGS. 1(a) and 1(b).

Specifically, on the substrate 1, the tracks 2 for the servo purpose areformed by lands and grooves in the concentric or spiral configuration.The widths of the tracks for the lands and grooves are set to be thesame for making the size of signals equal. On the tracks 2, theaddresses 3 written with the information of the tracks 2 and sectors areformed in the form of pits. In the optical disk substrate according tothe present invention, these addresses 3 are provided on the tracks 2for the lands and grooves. The difference of the single-sided opticaldisk substrate from the double-sided optical disk substrate resides inthe arrangement of the pit rows for the addresses 3. According to thepresent embodiment, correspondence of the concave and convex portions ofthe pit rows to the information is the same at the A and B portions,with the direction of disposition at the starting and end of theinformation being also the same. As a result, since the signals from theaddress pit rows formed in the tracks for the lands and grooves becomethe same, reading of the address may be effected by one circuit.Moreover, the pit rows for the addresses are disposed on the radiallines passing through the center of the substrate. This arrangement hasfor its object to reduce the time required for the retrieval bycalculating and specifying the positions on the disk from the addressinformation.

In the case where the address pit row of the tracks for the lands andthat of the tracks for the grooves are located approximately in the sameposition as in the conventional arrangement, the information of theaddress pits of the neighboring tracks leaks in as a crosstalk duringreading the information of the address pits, thus making it impossibleto read.

According to the present invention, however, since the positions of theaddress pit rows are spaced apart in the circumferential directionbetween the lands and grooves, the crosstalk may be alleviated so as toallow the address information to be read. As the result of investigationinto the crosstalk, in the case where an active layer of a phase-changematerial was used on a polycarbonate substrate having the width of thetracks for the lands and grooves at 0.8 μm in an optical system with thewavelength of 830 nm, and aperture number of the objective lens of 0.5,the crosstalk from the neighboring track was less than -30 dB when thedifference in height between the land and groove was larger than 50 nm.

Moreover, it has also been found that the length of time as the signalof the address pit row with respect to the maximum control frequencyband for the tracking should be less than four times for making itpossible to be controlled. For example, in the case where the maximumcontrol frequency band for the tracking is 3 KHz, the time length may beless than 83 μs.

In the substrate according to the present invention, it is preferablethat the amount of spacing in the circumferential direction, in thepositions of the addresses of the tracks for the lands and groovesshould be selected to be in the range of 1/4 sector to 3/4 sector, andmore preferably, at 1/2 sector.

The relationship between the optical disk and the read/write head is thesame as that shown in FIG. 12.

One example for change-over of the tracks between the lands and groovesis shown in FIG. 3.

In FIG. 3, the solid lines in the radial direction show the positions ofaddresses on the tracks for the lands, while the dotted lines representthe positions of addresses on the tracks for the grooves, and the amountof deviation of addresses between the tracks for the lands and groovesis set to be equivalent to 1/2 sector. Therefore, in the above case, thetime required for the change-over between the tracks for the lands andgrooves is to be the time for the disk to move through the amountequivalent to 1/2 sector, and thus, becomes shorter than the time forone sector in the conventional arrangement.

In the case where the change-over of the track is effected between thelands and grooves, since the address of the subsequent track is readafter having read the address in the previous track, it is necessarythat the deviation amount of the addresses between the tracks is set tobe at least longer than the length of the address.

As described earlier, with reference to the double-sided disk substrate,the identification of the tracks for lands and grooves provided on thesubstrate may be effected by using the tracking error signal and thesingle differential signal of the tracking error signal. Fundamentally,it is to be distinguished whether the point is to zero crossing pointrising at the right or the zero crossing point lowering at the right.Since reading of the address is not required for the identification ofthe lands and grooves, processing may be effected in real time.

Moreover, even in the case where the change-over between the tracks forthe lands and the tracks for the grooves is to be effected by oneread/write head, it can be made only by the change-over of polarity forthe tracking. Therefore, such a change-over between the track for thelands and the track of the grooves located close to each other may beeffected in the waiting time for the disk to move through 1/2 sector.

The substrate can be prepared in the method similar to that describedearlier with reference to the double-sided disk substrate. The resinsubstrate is prepared by the injection compression molding method usingthe stamper, while the glass substrate may be produced by the sol-gelmethod or etching method.

In the optical disk for the single side access according to the firstembodiment of the present invention, at least an active layer isprovided on the optical disk substrate as shown in FIGS. 1(a) to 1(c).In this case, the optical disk may be in the double-sided structure orthe single-sided structure. As the result of investigation into thecrosstalk, in the case where an active layer of a phase-change materialwas used on the substrate having the width of the tracks for the landsand grooves at 0.8 μm in an optical system with the wavelength of 830nm, and aperture number of the objective lens of 0.5, the crosstalk fromthe neighboring track was less than -30 dB when the difference in heightbetween the land and groove was larger than 50 nm.

In the optical disk of the present invention, the active layer is notlimited to be of the phase-change material, but may be of a dyeingmaterial, optical magnetic material or the like.

Moreover, in the optical disk of the present embodiment, since thedifference in height between the land and the groove is small, even thedrive using one read/write head may be employed without changing theposition of focus between the land and groove.

In the substrate of the present embodiment, since the positions of theaddress pit rows of the tracks for the lands and grooves are spacedapart, the information of the addresses may be read although they areprovided next to each other, and thus, a high density recording twotimes that in the case where only the tracks for the lands or the tracksfor the grooves are employed, may be achieved.

By setting the amount of spacing of the addresses between the tracks forthe lands and the grooves to 1/2 sector, the time required for thechange-over of the tracks is reduced from the time for moving throughone sector in the conventional arrangement, to the time for movingthrough 1/2 sector.

Referring to FIG. 8, there is shown an optical disk substrate accordingto a fourth embodiment of the present invention.

In FIG. 8, on the substrate, the tracks for the servo purpose are formedby lands and grooves in the concentric or spiral configuration. Thewidths of the tracks for the lands and grooves are set to be the samefor making the size of signals equal. On the tracks, the addresseswritten with the information of the tracks and sectors are formed in theform of pits. In the optical disk substrate according to the presentinvention, these addresses are provided on the tracks for the lands andgrooves. The difference of the single-sided optical disk substrate fromthe double-sided optical disk substrate resides in the arrangement ofthe pit rows for the addresses. According to the present embodiment,correspondence of the concave and convex portions of the pit rows to theinformation is the same at the A and B portions, with the direction ofdisposition at the starting and end of the information being also thesame. As a result, since the signals from the address pit rows formed onthe tracks for the lands and grooves become the same, reading of theaddress may be effected by one circuit. Moreover, the pit rows for theaddresses are disposed on the radial lines passing through the center ofthe substrate. This arrangement has for its object to reduce the timerequired for the search by calculating and specifying the positions onthe disk from the address information.

According to the present embodiment, the addresses for the lands andgrooves, are formed on the alternately continuous tracks for lands andgrooves as the pit rows. In the case where the wavelength of theirradiation light is 830 nm, the aperture number of the objective lensis 0.5, and the width of the tracks at the land and groove is 0.8 μm,the difference in the height between the land and groove should belarger than 50 nm in the case where only the address portions arerepresented by the pits, and larger than 200 nm when the informationrecording utilizing pit row equiphase is effected for the data regionalso as in ROM, because the influence of the crosstalk of theinformation on the neighboring track is different, and in the recordingutilizing the phase difference, the tracking control is also largelyaffected since the tracking of the tracks for the lands and grooves iseffected through utilization of the phase difference.

Here, either one of the track for the land or the track for the groovemay be made into ROM, and in this case, the difference in height betweenthe land and the groove should be larger than 200 nm.

In the optical disk (single-sided high density disk) according to thesecond embodiment of the present invention, the optical disk substrateas shown in FIG. 5 is used, and at least an active layer is provided onsaid optical disk substrate.

In this embodiment, since the difference in the heights is providedbetween the neighboring tracks for the lands and grooves, the crosstalkby the information of the next track is reduced during reading of theinformation of the tracks for the lands and grooves, and stable readingof the information can be achieved. Moreover, since the neighboringtracks for the lands and grooves are utilized, the high densityrecording two times that in the case where only the tracks for the landsor the tracks for the grooves are read can be effected.

The amount of spacing of the address positions between the tracks forthe lands and the tracks for the grooves should preferably be 1/4 sectorto 3/4 sector, and more preferably, be 1/2 sector. When the amount ofspacing is set to be 1/2 sector, the time required for the change-overof the tracks is reduced from the time required for the disk to movethrough 1 sector as in the conventional practice to the time for movingthrough 1/2 sector.

Meanwhile, for utilizing the optical disk of the present invention as aROM disk, it may be so arranged to provide a reflective layer.

In the case of the substrate according to the present invention havingdata pits for ROM only on the tracks for the lands, or on the tracks forthe grooves, or part of the tracks, an active layer at least capable ofrecording or rewriting is to be formed. By this arrangement, a diskhaving a ROM region and a recordable region or that having a ROM regionand a rewritable region can be obtained.

The reason for forming the tracks by the plurality of sectors is, on onehand, to improve accuracy of the fundamental clock and synchronizationfor reduction of signal jitter during rewriting of marks andreproduction so as to obtain higher reliability during rewriting ofinformation and reproduction, and on the other hand, to facilitate theaccess to any desired position on the disk by the address designationand address search or retrieval. The tracks are formed by the lands andgrooves to effect the tracking. The widths of the lands and grooves areset to be generally equal to each other so as to make the size of thesignals approximately equal to each other during formation of the markson the lands and grooves.

According to the present invention, the pit rows having such informationas the track address and sector addresses, etc. to be formed on theplurality of tracks for the lands, are disposed on approximately thesame radial line passing through the center of the substrate, while theaddress pit rows of the tracks for the grooves between the lands aredeviated in one direction on the same track and provided onapproximately the same but different radial line passing through thecenter of the substrate. As a result, the reading is not affected by thepit rows of the neighboring track during reading of the informationconstituting of pit rows, and thus, the reading or the address isfacilitated. Moreover, for change-over of the data between the tracksfor the lands and grooves, the address pit row is to be encounteredbefore moving through 1 sector, and the waiting time is reduced formaking it possible to change-over of the data at higher speed than inthe conventional arrangement. The reason for disposing the pit row ofthe addresses on the radial line passing through the center of thesubstrate is to specify the position on the disk by the addressinformation for reduction of the time required for the retrieval.

In the substrate used for the present invention, both in the case of thedouble-sided disk and the single-sided disk, the positions where theaddress information pit rows on the tracks for the lands (solid lines)are present and the positions where the address information pit rows onthe tracks for the grooves (dotted lines) are present, are arranged inthe similar radial line shape from the inner circumference to the outercircumference of the substrate. However, it is not necessarily requiredto make the amount for the one circumference of the track into the samenumber of sectors from the inner circumference to the outercircumference as shown in FIG. 3. As shown in FIG. 9, it may be soarranged to divide the data region on the disk into a plurality ofblocks from the inner circumference to the outer circumference, and toalter the number of sectors for one circumference of the track with theblocks. In this case, if the information in the sector is constant, thenumber of sectors can be increased towards the outer circumference,thereby to increase the recording capacity for the one substrate.

Moreover, the correspondence of the concave and convex portions and theinformation of the address pits provided on the lands and grooves ismade the same in the case of the access system only at one side of theoptical disk, and is inverted in the case of the double-side access. Asa result, when the correspondence between the concave and convexportions and information of the address pits is observed from theincident direction of light, it becomes the same. Therefore, in thiscase, one circuit system is sufficient for reading the address pitinformation, and thus, the construction is simplified.

Furthermore, since the film formation corresponding to the front andreverse faces of the optical disk can be effected by one series ofsteps, labor time is decreased for a cost reduction. By the employmentof different neighboring tracks on the front and reverse faces of theoptical disk, there is no possibility of heat interference, andrecording and erasing of the marks, etc. may be stably effected.

Although the present invention has been fully described by way ofexample with reference to the accompanying drawings, it is to be notedhere that various changes and modifications will be apparent to thoseskilled in the art. Therefore, unless otherwise such changes andmodifications depart from the scope of the present invention, theyshould be construed as being included therein.

What is claimed is:
 1. An optical disk substrate which comprises aplurality of sectors, tracks alternately formed into lands and groovesin a direction intersecting at right angles with a tracing directionduring recording or reproducing of information, a first pit row havingaddress information and formed at a specific position of the track of apredetermined one land or groove, and a second pit row having addressinformation and formed in a different track neighboring said trackformed with said first pit row in the tracing direction, and formed at aposition which is spaced apart by a distance which is longer than alength of the pit row from said specific position;wherein the deviationin distance between the pit rows of said neighboring tracks is in therange of 1/4 sector to 3/4 sector.
 2. An optical disk which comprises anoptical disk substrate including a plurality of sectors, tracksalternately formed into lands and grooves in a direction intersecting atright angles with a tracing direction during recording or reproducing ofinformation, a first pit row having address information and formed at aspecific position of the track of a predetermined one land or groove,and a second pit row having address information and formed in adifferent track neighboring said track formed with said first pit row inthe tracing direction, and formed at a position which is spaced apart bya distance which is longer than a length of the pit row from saidspecific position, and at least an active layer provided on said opticaldisk substrate;wherein the deviation in distance between the pit rows ofsaid neighboring tracks is in the range of 1/4 sector to 3/4 sector. 3.An optical disk Substrate which comprises a plurality of sectors, tracksalternately formed into lands and grooves in a direction intersecting atright angles with a tracing direction during recording or reproducing ofinformation, a first pit row having address information and formed at aspecific position of the track of a predetermined one land or groove,and a second pit row having address information and formed in adifferent track neighboring said track formed with said first pit row inthe tracing direction, and formed at a position which is spaced apart bya distance which is longer than a length of the pit row from saidspecific position;wherein correspondence of the address information tothe concave and convex portions of said pit rows is inverted betweensaid neighboring tracks; and wherein the deviation in distance betweenthe pit rows of said neighboring tracks is in the range of 1/4 sector to3/4 sector.
 4. An optical disk which comprises an optical disk substrateincluding a plurality of sectors, tracks alternately formed into landsand grooves in a direction intersecting at right angles with a tracingdirection during recording or reproducing of information, a first pitrow having address information and formed at a specific position of thetrack of a predetermined one land or groove, and a second pit row havingaddress information and formed in a different track neighboring saidtrack formed with said first pit row in the tracing direction, andformed at a position which is spaced apart by a distance which is longerthan a length of the pit row from said specific position, correspondenceof the address information to the concave and convex portions of saidpit rows being inverted between said neighboring tracks, and at leasttwo active layers and a reflective layer disposed between said activelayers;wherein the deviation in distance between the pit rows of saidneighboring tracks is in the range of 1/4 sector to 3/4 sector.
 5. Anoptical disk substrate which comprises a plurality of sectors, tracksalternately formed into lands and grooves in a direction intersecting atright angles with a tracing direction during recording or reproducing ofinformation, a first pit row having address information and formed atspecific position of the track of a predetermined one land or groove,and a second pit row having address information in a different trackneighboring said track formed with said first pit row, and formed in thetracing direction at a position which is spaced apart by a distancewhich is in a range of 1/4 sector to 3/4 sector from said specificposition.
 6. An optical disk substrate which comprises a plurality ofsectors, tracks alternately formed into lands and grooves in a directionintersecting at right angles with a tracing direction during recordingor reproducing of information, a first pit row having addressinformation and formed at specific position of the track of apredetermined one land or groove, and a second pit row having addressinformation in a different track neighboring said track formed with saidfirst pit row, and formed in the tracing direction at a position whichis spaced apart by a distance which is in a range of 1/4 sector to 3/4sector from said specific position, wherein correspondence of theaddress information to said pit row is inverted between said first pitrow and said second pit row.
 7. An optical disk substrate whichcomprises a plurality of sectors, tracks alternately formed into landsand grooves in a direction intersecting at right angles with a tracingdirection during recording or reproducing of information, a first pitrow having address information and formed at specific position of thetrack of a predetermined one land or groove, and a second pit row havingaddress information in a different track neighboring said track formedwith said first pit row, and formed in the tracing direction at aposition which is spaced apart by a distance which is in a range of 1/4sector to 3/4 sector from said specific position, wherein at least anactive layer is provided on said optical disk substrate.
 8. An opticaldisk substrate which comprises a plurality of sectors, tracksalternately formed into lands and grooves in a direction intersecting atright angles with a tracing direction during recording or reproducing ofinformation, a first pit row having address information and formed atspecific position of the track of a predetermined one land or groove,and a second pit row having address information in a different trackneighboring said track formed with said first pit row, and formed in thetracing direction at a position which is spaced apart by a distancewhich is in a range of 1/4 sector to 3/4 sector from said specificposition, wherein correspondence of the address information to said pitrows is inverted between said first pit row and said second pit row, andat least two active layers, and a reflective layer disposed between saidactive layers are provided on said optical disk substrate.